On many many occasions, Zombie ai will glitch into the players personal bubble making it impossible to block attacks while they ruin your gear.

Usually this is a running attack (probably the runner zeds)
From the front, they seem to sprint right into the player if not blocking.
And just starts beating the player while out of view.

Turning around feels impossible as the zombie is usually under your vision.

Player basically needs to run away quickly to evade the beat down.